How to display nested list and maintain MVC pattern?

问题

Attempting to display nested list using MVC 6 and EF code first design. I'm using this Tutorial to get me started with MVC and am trying to take it to another level.

Classes:

public class Location
{
    [Key]
    public int ID { get; set; }
    public string LocationName { get; set; }
    public ICollection<SubLocation> Sublocations { get; set; }
    }
}

public class SubLocation
{
    public int ID { get; set; }
    public string SubLocationName { get; set; }
}

Running dnx ef database update sets up my EF database correctly and assigns a foreign key to LocationID under SubLocation.

Now I want to display Sub Locations under each Location like the following image. The user can add new locations or sub locations tied to a location.

Displaying the list of locations is simple: return View(_context.Location.ToList());

To display the nested list of sub-locations, should I do the work in the controller or view?

I was hoping I could just use the view like the following but item.Sublocations is null for a reason that I'm not sure of since there is data in the database.:

@foreach (var item in Model) {
  <tr>
    <td>@Html.DisplayFor(modelItem => item.LocationName)</td>
  </tr>

  @foreach (SubLocation itm in item.Sublocations)
  {
    <tr>
        <td>@itm.SubLocationName</td>
    </tr>
  }
}

I've tried creating a query in the controller but the foreign key isn't available to compare against.

var test = (from m in _context.SubLocation
            where m.LocationID == curLocID   <-- m.LocationID isn't available
            select m.SubLocationName
            ).ToList();

Even if I could use the LocationID I'm not sure how to send the current Location (curLocID) from the View back to the controller. I think I need a helper method but I'm starting to go in circles.

How can I maintain proper MVC and display nested list from a subclass of my main class?

回答1:

You should consider adding a LocationID property to your SubLocation class which will be the foreign key to the Location table.

public class SubLocation
{
    public int ID { get; set; }
    public string SubLocationName { get; set; }
    public int LocationID { set;get;}
}

Now, query the locations. Location has a SubLocations property,so your view should work fine.

var locations = _context.Locations.Include(s=>s.SubLocations).ToList();
return View(locations);

来源：https://stackoverflow.com/questions/36633116/how-to-display-nested-list-and-maintain-mvc-pattern

标签

asp.net-mvc

entity-framework